Composite biocidal particles

ABSTRACT

A biocidal composition is disclosed comprising composite particles, each of the composite particles containing a shell and a core, the core comprising a metal or a metal-containing compound wherein the metal is a moiety selected from the group consisting of zinc, copper, bismuth, silver, zirconium, and combinations thereof, the shell comprising a pyrithione adduct comprising the reaction product of pyrithione with a portion of the core metal or metal compound. In one aspect, an anti-fouling composition is disclosed comprising (a) an anti-soft-fouling effective amount of copper pyrithione; and (b) an anti-hard-fouling effective amount of a copper-containing salt, or oxide or hydroxide thereof. The present invention also relates to a method of making an antifouling composition comprising particles of copper pyrithione and a copper-containing salt that is effective against hard-fouling and soft-fouling organisms.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to biocidal compositions, andmore particularly, compositions comprising composite particles, whereineach of the composite particles contains a shell and a core possessingdiffering biocidal activity profiles. The core comprises a biocidallyactive oxidized metal, or metal-containing compound, and the shellcomprises a pyrithione salt of the core metal having complimentarybiocidal activity to the activity of the core. Select compositions ofthe present invention, when incorporated into a matrix, such as a paintor other coating composition, provide the matrix with resistance tofouling by organisms of more than one type, thus providing broadspectrum biocidal activity.

2. Description of the Related Art

Certain composite particles containing a biocide are known. By way ofillustration, U.S. Pat. No. 5,510,109 discloses anantibacterial/antifungal material carried on a porous particle carrierthat is preferably a silica gel particle. As another illustration, U.S.Pat. No. 5,595,750 discloses an antimicrobial composition comprising aninorganic particle having a first coating possessing antimicrobialproperties and a second coating providing a protective function for thecomposition. Heretofore, however, no composite biocide particles havebeen known, based upon the knowledge of the present inventors,comprising two biocides with differing biocidal activity profiles.

In the marketplace, biocides enjoy wide usage. For example, biocidalcompositions are employed in a wide variety of applications, includingshampoos, soaps, skin care medicaments, as well as paints, particularlymarine paints. Fouling of marine equipment has been a persistent problemfor many years. For example, boat hulls, docks, buildings, fishnets andcages, and related marine equipment that are in constant contact withmarine water become fouled with algae, barnacles and other marineorganisms, and much time and expense is required to remove theseorganisms.

Generally, marine fouling has been categorized into two broad classes.“Soft-fouling” refers to growth of “soft” organisms, such as algae onmarine and coastal equipment and other outdoor structures. “Soft”organisms also include the fungi causing mildew, often co-existing withalgae, and typically necessitating the addition of both an algaecide anda fungicide in outdoor coatings such as architectural paints.“Hard-fouling”, by contrast, refers to growth of “hard” organisms suchas barnacles, and tubeworms. Compounds used to control hard foulinginclude copper, cuprous oxide, zinc oxide, and copper thiocyanate. Asused herein “anti-soft-fouling” refers to an antifouling agent that iseffective in reducing or preventing the growth of soft organisms,whereas “anti-hard-fouling” refers to an antifouling agent that iseffective in reducing or preventing the growth of hard organisms. Due tothe fact that there exist different organisms that cause soft-foulingversus hard-fouling, separate approaches have been taken to address eachtype of fouling.

Polyvalent metal salts of pyrithione (also known as1-hydroxy-2-pyridinethione; 2-pyridinethiol-1-oxide; 2-pyridinethione;2-mercaptopyridine-N-oxide; and pyridinethione-N-oxide) have gainedacceptance for use in marine paints and coatings to decrease or minimizesoft-fouling. These salts are known to be effective biocidal agents,leading to their wide usage as algaecides, fungicides and bactericidesin paints and personal care products such as anti-dandruff shampoos.Generally these salts are only sparingly soluble in water, as typifiedby magnesium pyrithione, barium pyrithione, bismuth pyrithione, ferricpyrithione, strontium pyrithione, copper pyrithione, zinc pyrithione,cadmium pyrithione, and zirconium pyrithione. The most widely useddivalent pyrithione salts are zinc pyrithione and copper pyrithione.Synthesis of polyvalent pyrithione salts is described in U.S. Pat. No.2,809,971 incorporated herein by reference in its entirety. Otherpatents disclosing similar compounds and processes for making theminclude U.S. Pat. Nos. 2,786,847; 3,589,999; 3,590,035; and 3,773,770,each of which is incorporated herein by reference in their entireties.

Zinc pyrithione is useful as an antimicrobial agent active againstgram-positive, some negative bacteria, fungi, algae and yeasts.Suspensions of zinc pyrithione are also used as antibacterial,antifungal, and antialgael additives to provide soft-fouling protectionfor paints and other coating compositions. However, zinc pyrithione isnot as effective against hard-fouling organisms as might be desired.

Copper pyrithione is sold commercially as an algaecide andanti-soft-fouling agent for marine paints and coatings as disclosed inU.S. Pat. Nos. 5,246,489 and 5,540,860, both of which are incorporatedby reference in their entireties. Copper pyrithione offers severaladvantages over zinc pyrithione for many applications, notably a lowersolubility (about 1 ppm versus 6-10 ppm for zinc pyrithione). The lowersolubility of copper pyrithione, as compared to zinc pyrithione,increases its effective availability as a biocidal agent over a longerperiod of time when exposed to marine environments, and makes itparticularly desirable as an anti-soft-fouling agent. However, copperpyrithione is not as effective in preventing hard-fouling as might bedesired. To address this shortcoming, combinations of soft-fouling andhard-fouling agents have been manufactured. However, to date, thesecombinations have not been entirely successful.

Combinations of zinc pyrithione or copper pyrithione and coppercompounds such as cuprous oxide, copper hydroxide, or copper thiocyanateare known to be useful antifouling agents when formulated into marinepaint compositions to control both hard- and soft-fouling. Such a paintcomposition is disclosed in U.S. Pat. No. 5,057,153, herein incorporatedby reference in its entirety. However, paint compositions which includezinc pyrithione and cuprous oxide antifouling agents tend to formundesirable gels during storage, thereby limiting the useful life of thecomposition. The gelation problem, and efforts to resolve or mitigate itare described in U.S. Pat. Nos. 5,298,061 and 5,342,437.

Tributyl tin compounds have in the past been demonstrated to beeffective in controlling soft-fouling, and to a lesser degree,hard-fouling, organisms. However, tributyl tin compounds are toxic tonon-target organisms, and are persistent, thus posing an unwantedenvironmental hazard.

In addition, these toxic compounds persist in the environment afterapplication and continue to exert their toxic effects for years.Therefore, use of tributyl tin compounds as antihard- andantisoft-fouling agents is restricted in many parts of the world.Accordingly, what the paints and coatings community needs is a saferantimicrobial agent that is effective in controlling both soft- andhard-fouling growth simultaneously. In this regard, zinc and coppercompounds, such as zinc oxide, cuprous oxide, and pyrithione salts, suchas zinc pyrithione or copper pyrithione, have been individually added toantifouling paints. However, such a combination made by separatelyadding these two components to a paint has been found to provide lessperformance efficacy (based upon the amounts of individual componentsadded to the paint) than might otherwise be desired. Accordingly, newmethodology for providing relatively environmentally safe combinationsof anti-hard and anti-soft components within a single biocidalcomposition package for use in paints and other coatings would be highlydesired by the coatings manufacturing community. The present inventionprovides one answer to that need.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a biocidal compositioncomprising composite particles, each of said composite particlescontaining a shell and a core, said core comprising a metal or ametal-containing compound wherein the metal is a moiety selected fromthe group consisting of zinc, copper, bismuth, silver, zirconium, andcombinations thereof, and said shell comprising a pyrithione adductcomprising the reaction product of pyrithione with a portion of saidmetal or metal-containing compound from said core. The shell componentprovides complimentary biocidal activity to the biocidal activity of thecore component.

In another aspect, the present invention relates to a biocidalcomposition that is effective against both soft fouling and hard foulingcomprising composite particles, each said composite particle containinga shell and a core, said core comprising a metal or a metal-containingcompound comprising a moiety selected from the group consisting of zinc,copper, bismuth, silver, iron, titanium, aluminum, zirconium andcombinations thereof, and said shell comprising a pyrithione saltcomprising pyrithione and said moiety.

In yet another aspect, the present invention relates to a method ofmaking a biocidal composition comprising reacting pyrithione or awater-soluble salt of pyrithione and an essentially water insolublemetal or metal-containing compound (such as a copper salt, oxide orhydroxide), optionally in the presence of a surfactant, to produce acomposition comprising the above described composite particles. In oneapplication, the resulting composition is advantageously effectiveagainst hard-fouling and soft-fouling organisms.

In still another aspect, the present invention relates to a method ofreducing or inhibiting the growth of hard and soft organisms on asurface which comprises contacting the surface with an antifoulingcomposition comprising the above-described composite particles.

In another aspect, the present invention relates to a shampoo, soap,skin care medicament, or combination thereof, comprising a surfactantand composite particles, each said composite particle containing a shelland a core, said core comprising a metal or a metal-containing compoundcomprising a moiety selected from the group consisting of zinc, copper,bismuth, silver, iron, titanium, aluminum, zirconium and combinationsthereof, and said shell comprising a pyrithione salt comprisingpyrithione and said moiety. When employed for this purpose, thecomposite particles offer the potential for reduced skin absorption andequivalent skin or hair surface coverage vis-à-vis a simple mixture ofthe biocidal additives.

In still another aspect, the present invention relates to a coatingcomposition comprising an aqueous base medium (such as a latex) or anorganic solvent based resin-containing base medium and an antifoulingcomposition comprising the above-described composite particles.

In yet another aspect, the present invention relates to a coatedsubstrate comprising a substrate and a coating thereon, said coatingcomprising the above-described composite particles.

These and other aspects will become apparent upon reading the followingdetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a comparison photomicrograph of cuprous oxide particles viewedat 5,000× magnifications.

FIG. 2 is a photomicrograph of composite particles of the presentinvention containing a core of cuprous oxide and a shell of copperpyrithione prepared by the method of the invention and viewed at 5,000×magnifications.

DETAILED DESCRIPTION OF THE INVENTION

It now has been surprisingly found, in accordance with the presentinvention, that a solution is provided to the problem of controllingboth soft-fouling and hard-fouling marine organisms in a single biocidalcomposition comprising composite particles. Select composite particlesprovide antifouling efficacy against both hard-fouling and soft-foulingorganisms that are typically encountered in a marine environment. Thecomposite particle structure has been found to be particularly effectivein providing controlled release of the core biocide into the aqueousenvironment that is present under use conditions for a marine orarchitectural paint or a personal care composition such as soap orshampoo. As another alternative, composite particles are suitablydesigned to provide a relatively low-cost biocide by transchelation toprovide composite particles having a core of filler or a biocide and ashell of pyrithione, thereby increasing the effective surface area ofthe pyrithione biocide. When employed in personal care compositions, thecomposite particles can provide desirable reductions in skinabsorptivity relative to a mixture of the individual biocidalcomponents. The composite particles prepared in accordance with thepresent invention are also advantageously employed in marine paints,architectural coatings and adhesives and the like, but they also can betailored for use in other applications such as in personal care items,such as soaps, shampoos and skin care medicaments, and suitable plasticand polymeric substrates. The particle size for the composite particlestypically ranges from 1 to 20 microns, advantageously from 1 to 10microns, in diameter.

The compositions of the present invention avoid the toxicity issuestypically associated with tributyl tin compounds currently used tocontrol both hard- and soft-fouling marine organisms. In addition, thecompositions of the present invention resist gelation during storage,and therefore can be stored for long periods of time prior to use. Thecompositions of the present invention provide the additional advantageof a more economical and environmentally preferred rate of delivery ofthe antifouling components, namely the copper pyrithione component andthe copper or oxide or hydroxide component. In one embodiment, cuprousoxide and sodium pyrithione are mixed in an aqueous solvent to produce acomposite particle comprising a mixture of copper pyrithione and cuprousoxide wherein the cuprous oxide core is coated with a shell of copperpyrithione.

As used herein, the term “antifouling agent” refers to compounds whichsubstantially reduce or eliminate the growth of marine organisms thatattach to structures in contact with marine water. The term“soft-fouling” and “soft-fouling organisms” as used herein refers tothose soft marine organisms such as algae, slime, grass and diatoms. Theterm “hard-fouling” and “hard-fouling organisms” as used herein refersto hard or shelled marine organisms such as barnacles, mussels, bryozoaand tubeworms. The term “anti-soft-fouling effective amount” refers toan amount of a compound which is effective in substantially reducing oreliminating the growth of soft-fouling organisms. Similarly, the term“anti-hard-fouling effective amount” refers to an amount of a compoundwhich is effective in substantially reducing or eliminating the growthof hard-fouling organisms.

As indicated above, the invention relates to an antifouling agent,comprising an antisoft-fouling effective amount of copper pyrithione;and an antihard-fouling effective amount of a copper-containing salt.

Copper pyrithione is among the least water soluble of the pyrithionesalts (generally less than 1 ppm in seawater). The zinc salt, bycomparison, has a water solubility of about 6-10 ppm, while the sodiumsalt of pyrithione has a water solubility of about 53% by weight. Copperpyrithione is, therefore, a very desirable component of antifoulingmarine paints due to its relative insolubility but adequate biocidalefficacy.

The copper-containing core-compound can be a copper or one of itscompounds slightly soluble in water up to about 10 ppm. Usefulcounterions for the copper cation include oxides, sulfides andselenides. Preferable copper-containing compounds that are useful in theinvention include cuprous oxide, cuprous sulfide, copper thiocyanate,and copper hydroxide, or copper metal, either coated or uncoated, orsurface oxidized. A particularly preferable copper-containing compoundis cuprous oxide. Combinations of these copper-containing compounds mayalso be used in accordance with the invention.

When working with copper compounds, an effective combination of copperpyrithione and another copper-containing salt, oxide, or hydroxidethereof (or copper metal or surface-oxidized copper) is employed in theantifouling composition of the present invention to provide the desiredantifouling protection. Preferably, the relative proportions of copperpyrithione and copper containing compound are such that the copperpyrithione partially or completely coats the other copper containingcompound to form a shell around that other compound. To achieve thisresult, the copper-containing metal, oxide, or hydroxide (or combinationthereof) component of the antifouling composition of the inventionpreferably comprises from about 99 to about 60% by weight, morepreferably 98 to about 80% by weight, and most preferably 98 to about90% by weight, all based on the total weight of said antifouling agent,and the copper pyrithione component of the antifouling agent of theinvention preferably comprises from about 1 to about 40% by weight, morepreferably from about 2 to about 10% by weight, and most preferably fromabout 2 to about 10% by weight, all based on the total weight of saidantifouling agent.

A surfactant or fatty acid may be included in the antifouling agent ofthe invention to coat the particles to prevent the copper-containingcore compound from oxidizing upon exposure to air. Suitable fatty acidsand derivatives for use in the present invention include oleic acid,stearic acid, glycerol, lecithin and the like.

The antifouling composition of the invention may be prepared by atranschelation reaction of pyrithione or a water-soluble salt ofpyrithione and a copper-containing minimally soluble salt, or a copperparticle. Pyrithione may be used in its acid form, or it may be employedin the form of a water-soluble salt of pyrithione for the desiredtranschelation reaction. Preferably, the water-soluble salt ofpyrithione has a water solubility greater than about 4 ppm. Useful watersoluble salts of pyrithione preferably include an ammonium ion or analkali or alkaline earth metal ion such as sodium or calcium, ormagnesium. Accordingly, exemplary water soluble salts of pyrithioneinclude sodium pyrithione, potassium pyrithione, lithium pyrithione,ammonium pyrithione, tert-butyl amine pyrithione, calcium pyrithione,dithiobis (pyridine-N-oxide), a magnesium salt adduct of dithiobis(pyridine-N-oxide), and combinations thereof, to cause transchelation ofsaid pyrithione compound to copper pyrithione. The most preferredwater-soluble salt of pyrithione useful in the present invention is thesodium salt (i.e., sodium pyrithione). The amount of pyrithione orwater-soluble salt of pyrithione can vary over a wide range andestablishing a useful amount is within the capabilities of the ordinaryskilled practitioner based on the stoichiometry of the reaction.

As indicated above, suitable copper-containing compounds and hydroxidesthat are useful in the present invention include cuprous oxide, cuproussulfide, copper thiocyanate, copper, surface oxidized copper, partiallyreduced cupric oxide, and copper hydroxide. A particularly preferablecopper-surface oxidized copper, containing salt is cuprous oxide. Theamount of copper-containing salt present in the reaction may varydepending on the amount of pyrithione or water-soluble salt ofpyrithione used in the reaction.

Sufficient pyrithione, or water-soluble salt of pyrithione, must beadded to the particle forming reaction to produce enough copperpyrithione to protect against soft-fouling microorganisms and alsoenough copper-containing salt, hydroxide, or oxide (e.g., cuprous oxide)to be effective against hard fouling organisms, present within a weightrange of ratios of from 1:20 to 20:1 (more preferably of from 1:10 to10:1) of copper pyrithione relative to the copper-containing salt, oroxide or hydroxide thereof. Preferably, the relative proportions ofcopper pyrithione and copper containing salt are such that the copperpyrithione partially or completely coats the cuprous oxide particle.

Useful media for the reaction include aqueous media such as water, orwater in combination with one or more organic solvent(s). Useful organicsolvents include alcohols, such as methanol, ethanol, amines such asdiethanolamine, ether, esters, and the like, including emulsifiedcombinations of same.

In accordance with the method of the invention, the copper-containingsalt and pyrithione or water-soluble salt of pyrithione are mixed in asolvent such as water to produce a mixture of copper pyrithione andcopper-containing compound, and preferably, a copper-containing saltparticle that is coated with copper pyrithione molecules.

Additional materials, such as dispersants, surfactants, and the like maybe added to the reactants during the precipitation or transchelationreaction to prevent agglomeration of the pyrithione salt particles.Alternatively, the dispersant or surfactant may be added at thecompletion of the reaction to prevent particle agglomeration. Exemplarydispersants include linear alcohol alkoxylates, such as the linearalcohol ethoxylates, ethyoxylated/propoxylated block copolymers,ethyoxylated/propoxylated fatty alcohols, and polyoxyethylene cetylethers, and the like. If desired, the alcohol alkoxylate is suitablyend-capped with a lower alkyl group, and such a product is commerciallyavailable as POLY-TERGENT SLF-18 surfactant, available from BASFCorporation. Useful anionic surfactants include alkyl diphenyletherdisulfonates, alkyl phenyl ethoxylated phosphate esters, carboxylatedlinear alcohol alkoxylates, linear alkyl benzene sulfonic acid,diisobutyl sulfosuccinate, and alkyl sulfonates.

Other useful anionics are polycarboxylated alcohol alkoxylates,preferably those selected from the group consisting of the acids ororganic or inorganic salts of the following: polycarboxylated linearalcohol alkoxylates, polycarboxylated branched alcohol alkoxylates,polycarboxylated cyclic alcohol alkoxylates, and combinations thereof.

Illustrative cationic dispersants include alkyl triammonium halide,non-linear alkyl dimethyl halide and alkyl dimethyl benzyl ammoniumhalide-containing surfactants. Illustrative amphoteric dispersantsinclude polyglycol ether derivatives, ethoxylate oxazoline derivatives,lauramidopropyl betaine and lecithin.

As will be appreciated by those skilled in the art, suitable blends canbe employed in the process of the present invention based on variouscombinations of the above-described surfactants. The dispersant orsurfactant is preferably employed in a total amount of between about0.05 and 10%, more preferably between about 0.1 and 5%, most preferablybetween about 0.5 and about 1.5% by weight, based on the total weight ofthe reaction mixture.

A fatty acid, as described above, may be included in the antifoulingagent of the invention to coat the particles to prevent thecopper-containing salt from oxidizing upon exposure to air. The fattyacid component may be added to the reaction mixture, or after theparticles are isolated, as described in more detail below.

Preferably, the temperature of the reaction should be maintained betweenabout 20° C. and about 80° C., and most preferably between about 25° C.to about 70° C. A particularly useful temperature range is 40° C.-70° C.

The pyrithione composite particles may be isolated from the by-productsby filtration of other isolation methods known in the art.

General methods for making a copper-based version of an antifoulingagent of the invention include either (a) first producing a water slurryof cuprous oxide, desired aqueous slurry of cuprous oxide, and (b)adding sodium pyrithione, or a solution thereof, to this slurry, tocause transchelation of the sodium and surface generated copper ions andthereby produce adherent copper pyrithione. The sodium pyrithione can beused in crude form such as 15% plant stream in “as produced” or 40%purified form. The cuprous oxide/sodium pyrithione slurry is then mixedfor a time sufficient to enable all of the sodium pyrithione to reactand transchelate to form adherent copper pyrithione. The solids are nextwashed to remove any of the water soluble salts. The particles mayoptionally be coated with a fatty acid or other protectorant such aslecithin to prevent the cuprous oxide from oxidizing to cupric oxideonce dried. The product is then filtered, dried. The product is nowready for use in marine paints as an antifouling agent.

A preferred process for carrying out the present invention entails thesteps of: (1) charging into a reaction vessel an untreated cuprous oxideslurry, (2) adding crude sodium pyrithione, (3) mixing until all of thesodium pyrithione is reacted, (4) adding a small amount of protectiveagent to coat the particles, and (5) filtering, washing, drying andmilling the product.

Another preferred process for carrying out the present invention entailsthe steps of: (1) charging into a reaction vessel a fatty acid treatedcuprous oxide slurry, (2) adding crude sodium pyrithione, (3) mixinguntil all of the sodium pyrithione is reacted, (4) filtering, washing,drying and milling the product.

Another process for carrying out the present invention entails the stepsof: (1) charging into the reaction vessel some treated cuprous oxidepowder then adding water with stirring to make a slurry, (2) addingcrude sodium pyrithione, (3) mixing until all of the sodium pyrithioneis reacted, (4) filtering, washing, drying and milling the product.

Another process for carrying out the present invention entails the stepsof: (1) charging into the reaction vessel a treated cuprous oxideslurry, (2) adding commercial grade sodium pyrithione, (3) mixing untilall of the sodium pyrithione is reacted (4) filtering, washing, dryingand milling the product.

As another alternative, the composition of the present invention issuitably produced by combining copper pyrithione (in the form of anaqueous dispersion, wet cake or dry solid) with cuprous oxide, or by“co-streaming” the copper pyrithione into the cuprous oxide production.One advantage of using copper pyrithione rather than sodium pyrithione,is that essentially no sodium salts remain in the composition, thusobviating any need for water washing of the product to remove sodiumsalts.

The copper pyrithione/cuprous oxide composition of the invention isuseful as an antifoulant in marine paints and coatings, or as a seed andcrop fungicide.

EXAMPLES

The following examples are intended to illustrate, but in no way limitthe scope of, the present invention.

Example 1 Preparation of a 1:10 Parts by Weight CopperPyrithione:Cuprous Oxide Composite Particle Product Made Using CuprousOxide Plus Sodium Pyrithione

292.19 grams of a 70% aqueous untreated cuprous oxide slurry was chargedinto a 1000 ml 3-neck, round-bottom flask reactor, followed by additionof 117.28 grams of 16.1% sodium pyrithione solution. The reactionmixture was stirred continuously, and the pH of the mixture monitoredand recorded. The initial pH was 5, and it increased during the reactionto a final pH of 10.5 at room temperature. After approximately 4 hoursof mixing, the contents of the flask was assayed for sodium pyrithionecontent by adding iron chloride and looking for the blue color of ironpyrithione. However, no blue color was found, indicating that thereaction was complete. A small amount (0.5% by weight) of stearic acidwas added (to coat the particle) and mixed for 30 minutes.

The resulting copper pyrithione/cuprous oxide product was isolated byfiltration. The resulting cake was then washed with water until thefiltrate was free of ions as measured by conductivity. The cake was thendried in an vacuum oven at 30° C. overnight.

Microscopic examination indicated that many of the cuprous oxideparticles were coated with adhering particles of copper pyrithione toform the desired composite particles plus sodium pyrithione.

Example 2 Preparation of a 1:10 Parts by Weight CopperPyrithione:Cuprous Oxide Composite Particle Product Made Using CuprousOxide Plus Sodium Pyrithione

This Example followed the same procedure as in Example 1, except 292.19grams of a 70% aqueous fatty acid treated cuprous oxide slurry wascharged into a 1000 ml 3-neck, round-bottom flask reactor. The cuprousoxide had been treated with 0.5 weight percent of stearic acid. Noadditional fatty acid was added later to coat the product.

The composite particle product was examined under a microscope consistedof needle-shaped copper pyrithione particles, cuprous oxide particles,and cuprous oxide particles coated with copper pyrithione.

Example 3 Preparation of a 1:5 Parts by Weight Copper Pyrithione:CuprousOxide Composite Particle Product Made Using Cuprous Oxide Plus SodiumPyrithione

298.66 grams of a 70% aqueous fatty acid treated cuprous oxide slurrywere charged into a 1000 ml 3-neck, round-bottom flask reactor. 234.61grams of 16.1% crude sodium pyrithione solution were added, and thereaction mixture was continuously stirred as the pH of the mixture wasmonitored. After 4 hours of mixing the sodium pyrithione in the flaskwas assayed and found to be 0.0% indicating that the reaction wascomplete.

The resulting copper pyrithione/cuprous oxide composite product wasisolated by filtration. The resulting cake was then washed with wateruntil the filtrate was free of ions as measured by conductivity. Thecake was then dried in an vacuum oven at 30° C. overnight.

The microscopic examination result weakens the application as originallystated.

Example 4 Preparation of a 1:20 Parts by Weight CopperPyrithione:Cuprous Oxide Composite Particle Product Made Using CuprousOxide Plus Sodium Pyrithione

288.94 grams of a 70% aqueous fatty acid treated cuprous oxide slurrywas charged into a 1000 ml 3-neck, round-bottom flask reactor, followedby addition of 58.55 grams of 16.1% sodium pyrithione solution. Thereaction mixture was continuously stirred, the pH of the mixture wasmonitored, showing an initial pH of 5 and a final pH of 10.5. After 4hours of mixing, no sodium pyrithione was found in the flask indicatingthat the reaction was complete.

The resulting copper pyrithione/cuprous oxide product was isolated byfiltration. The resulting cake was then washed with water until thefiltrate was free of ions as measured by conductivity. The cake was thendried in an vacuum oven at 30° C. overnight.

Example 5 Efficacy Testing of Composite Particle Product

The antifouling efficacy of the composition of Example 1 was evaluatedby mixing 110 grams of it into 90 grams of a paint base. The commercialpaint comprised:

TABLE 1 PAINT FORMULATION INGREDIENT GRAMS PERCENT BENTONE SD-2thickener 1.7 0.85 VAGH* resin 4.99 2.50 CUPRIC PYRITHIONE TO CUPROUS110 55.00 OXIDE IN A WEIGHT RATIO OF 1:10 TRICRESYL PHOSPHATE 4.3 2.15WOOD ROSIN 10 5.00 SILICA 10.4 5.20 SOLVENT MIXTURE** 55.28 27.64DISPERBYK 163*** 3.33 1.67 TOTAL 200.00 100.00 *VAGH (polymer resin) =vinyl chloride-vinyl acetate-vinyl alcohol terpolymer, a product ofUnion Carbide Corporation. **The solvent mixture used was a mixture of40% by weight of xylene and 60% by weight of methyl-isobutyl ketone(MIBK) ***DIPERBYK 163 (dispersing agent) = a high molecular weightblock copolymer, a product of BYK-Chemie.

This paint was painted onto fiberglass panels (8″×10″) and (12″×6″),which were then submerged in under seawater for eight months (andrunning) in Miami, Fla. The results to date show:

(1) the composite particle product's combination of cupric pyrithioneand cuprous oxide is much more effective than either biocide alone andcomparable in efficacy to a paint made using a simple mixture of thesetwo biocides;

(2) relatively low level of cupric pyrithione (3%) and cuprous oxide(30%) containing paints in the composite particle perform better thanthe “cuprous oxide alone” controls;

(3) This composite particle product is effective in providing totalantifouling performance against hard and soft fouling.

Pictures in the form of microphotographs of the cuprous oxide particles,and of the composite cuprous oxide/copper pyrithione particles, areprovided in FIG. 1 and FIG. 2 respectively. FIG. 2 shows the attachmentof small copper pyrithione particles to the surface of larger cuprousoxide particles.

The composite particle configuration is believed to providecomplimentary biocidal efficacy for the following reason: CuPT is mosteffective against algae, while cuprous oxide provides complementaryperformance by strongly resisting barnacle formation but is relativelyineffective against algae. This combination product provided completecontrol of marine fouling after five months of exposure of the paintedfiberglass panels to seawater. Other than tributyl tin, no otherantifouling agent is known by the present inventors to provide thiseffectiveness against hard and soft fouling, and tin suffers from theabove-described environmental problems.

PROPOSED EXAMPLES Proposed Example 6 Composite Particles are PreparedUsing Aluminum Oxide Plus Sodium Pyrithione

A beaker with a stirrer is charged with a slurry of 10.0 g (0.10 m) ofaluminum oxide in 100 ml of distilled water. To this stirred slurry, atambient temperature, is added dropwise over a period of one-half hour11.8 g, 0.029-mole of a 40% solution of the sodium salt of 2-pyrithione.This mixture is stirred an additional 1 hr. at ambient temperature, thepH adjusted to 8.5 with dilute hydrochloric acid, and the slurry isfiltered, washed with 3 times 50 ml of distilled water, or untilessentially free of soluble pyrithione salt. It is then dried in a 40-50C oven overnight to yield 11.2 g powder. XRF analysis of the resultingcomposite composition indicates the presence of a pyrithione-containingcoating on the water-insoluble core aluminum oxide substrate. The newcomposition also shows enhanced bioactivity toward algae, fungi, andbacteria, relative to the core material, when challenged in standardtests for such activity.

Proposed Examples 7-23 Composite Particles are Prepared Using VariousMetals, Metal Oxides or Metal Salts Plus Sodium Pyrithione

Following the procedure of Example 6 above, the amount of the metalelement or compound described in Table 2 is employed instead of thealuminum oxide used in Example 6. XRF analysis of the resultingcomposite composition powder (having a yield given in the last column ofTable 2 for each example) indicates the presence of apyrithione-containing coating on the water-insoluble core substrate. Thenew composition also shows enhanced bioactivity toward algae, fungi, andbacteria, relative to the core material, when challenged in standardtests for such activity.

TABLE 2 VARIOUS COMPOSITE PRODUCT COMBINATIONS SHELL COMPOUND COMPOSITESODIUM PRODUCT PYRITHIONE YIELD CORE REAGENT DRY COMPOUND 40% aqueousWEIGHT COMPOSITION (grams) (grams) (grams) 7 Aluminum phosphate 10 9.911.1 8 Bismuth Oxide 10 9.9 10.4 9 Copper 10 12.8 11.5 10 Copper IICarbonate 10 4.3 10.5 11 Cuprous Oxide 10 5.6 10.7 12 Cupric Oxide 1010.1 11.2 13 Copper I Selenide 10 5.6 10.7 14 Iron II Oxide 10 11.2 11.815 Iron III Oxide 10 5.0 10.9 16 Silver 10 3.7 10.7 17 Silver Oxide 101.7 10.3 18 Titanium Oxide 10 20.2 12.1 19 Zinc 10 12.3 11.5 20 ZincOxide 10 9.9 11.2 21 Zinc Selenide 10 5.6 10.7 22 Zirconium Oxide 1013.1 11.4

Proposed Example 24 Preparation of a Shampoo

An antidandruff shampoo is prepared using the composite biocideparticles described in Example 20 having a core of zinc oxide and ashell of zinc pyrithione. The shampoo contains the following components:

Component A: Magnesium aluminum silicate 1.0% Water 41.0% Hydroxypropylmethylcellulose 0.8%

Component B: Zinc Pyrithione/zinc oxide composite particles, 4.0%Component C: Cocamide DEA 1.0% Component D: Triethanolamine laurylsulfate, 40% 40.0% Triethanolamine, 99% 3.2% FD&C Blue No. 1 (0.2%) 1.5%FD&C Yellow No. 5 (0.1%) 0.5% Fragrance q.s.

The antidandruff shampoo composition was made as follows:

Component A was prepared by heating water to 70° C. and dissolving theother two components with stirring (about 1500 rpm). Component B wasadded, and stirring continued for 5 minutes. Stirring speed was reducestirring to ˜300 RPM. Component C was melted in a separate container,and added to the A/B mixture. The heat was removed and component D wasadded while the mixture cooled.

The present invention is intended to illustrate, but in no way limit thescope of the present invention. Although the invention has been shownand described with respect to illustrative embodiments thereof, itshould be appreciated that the foregoing and various other changes,omissions and additions in the form and detail thereof may be madewithout departing from the spirit and scope of the invention asdelineated in the claims. All patents and patent applications mentionedare herein incorporated by reference in their entirety.

1. A biocidal composition comprising composite particles, each of saidcomposite particles containing a shell and a core, said core consistingessentially of a metal element zinc or metal-containing compound zincselenide, and said shell consisting essentially of a metal pyrithioneformed by a transchelation reaction of sodium pyrithione with a portionof the metal element or metal-containing compound of said core in water.2. A biocidal composition comprising composite particles containing ashell and a core, said core consisting essentially of a metal elementzinc or a metal-containing compound zinc selenide and said shellconsisting essentially of a metal pyrithione formed by a transchelationreaction of sodium pyrithione with a portion of the metal element ormetal-containing compound of said core in water, wherein the particlesize for said composite particles ranges from 1 to 20 microns indiameter.
 3. A biocidal composition comprising composite particles, eachof said composite particles containing a shell and a core, said coreconsisting essentially of elemental zinc or zinc selenide, and saidshell consisting essentially of zinc pyrithione formed by atranschelation reaction of sodium pyrithione with a portion of theelemental zinc or zinc selenide of said core.
 4. The biocide compositionof claim 3 wherein the particle size for said composite particles rangesfrom 1 to 20 microns in diameter.